Snellen Plastic Eye Chart 20 Feet 22 x 11inches
Product Description
Snellen Plastic Eye Chart 20 Feet 22 x 11inches
- Snellen Eye Chart
- 20 Feet Distance Vision Eye Chart.
- Chart with Red Green Lines
- Snellen Wall Eye Chart, 22 in. x 11 in.
- Washable Eye Chart
The Snellen eye chart was originally introduced in 1862 by Herman Snellen. The Snellen eye test uses the idea of a subtended 5 minutes of arc with a 20 foot distance. This became the "standard vision" measurement. Also, Snellen developed the idea of a 5x5 grid for a standard for his optotypes. Each optotype must meet certain percentage requirements in this grid before it is used for testing. This helps to make a uniform and equal vision chart. The Snellen eye chart is the basis for many other vision tests.
Technical Specifications
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